1. Field of the Invention
The present invention relates to a system, method and program for network management, in particular to controlling access to web pages and email transmission/reception.
2. Description of the Related Art
TCP/IP (Transmission Control Protocol/Internet Protocol), which is a WWW (World Wide Web) communication protocol, is widely used to transmit and receive information over the Internet. When transmitting/receiving web data, HTTP (Hyper Text Transfer Protocol), which is defined as an upper layer of TCP/IP, is used. A client who receives service from a WWW server system inputs a URL (Uniform Resource Locator) into a WWW browser to access the web page (website) specified by the URL.
Access to web pages is usually unrestricted, so that users can browse various information published on web pages all over the world through the Internet. Accordingly, web pages are utilized not only in ordinary households, but also in educational institutions and business sectors. However, while the Internet is useful for obtaining information, its very capability of allowing users to browse information in an unlimited manner has its downsides as well. Examples of the downsides that have been pointed out include a difficulty in finding desired information from among the high amount of information that is available, access to harmful information by children and juveniles, and so on.
To this end, a technique has been developed for providing an appropriate restriction on web page browsing (Japanese Patent Laid-Open No. 2005-267015). This technique prevents users from browsing specific web pages by regulating access to the web pages based on registration information including the URLs of banned sites and those of approved sites, which have been registered in advance. This type of web page browsing restriction method is generally called “URL filtering”.
Meanwhile, email systems are known as another way to transmit/receive information over the Internet. The email system is a system that allows the exchange of data and messages with specific users through the Internet. The email system is used in various situations because it can be used with any terminal as long as the terminal can connect to the Internet.
However, it is known that the email system also has a downside associated with its convenience. For example, what is called spam (unsolicited email), which refers to email sent in bulk to recipients without their permission for the purpose of advertisement, promotion, solicitation and the like, has recently become a social problem. In light of such circumstances, a technique for blocking email addressed to unspecified recipients has been developed (Japanese Patent Laid-Open No. 2003-348166). This technique allows a server that transmits/receives email to/from a communication device to control the delivery of a received email to the recipient specified by the email based on whether or not the received email satisfies predetermined conditions. Another configuration is known in which emails transmitted/received in a network are classified so as to manage the email utilization status (Japanese Patent Laid-Open No. 2003-333100).
In order to restrict web browsing, quarantine a received email, or manage emails with the conventional techniques as described above, it is necessary to prepare a dedicated device for executing each process, such as a device for detecting who viewed what in order to restrict web browsing, and a device for viewing an email log in order to quarantine a received email. This increases the size of the system and requires a large installation space. Further, because security is essential for both devices, the administrator has to operate each device using an ID and a password, and perform an authentication operation on each device, which makes controlling and operating the device complicated.